What this test measures
Creatinine is a waste product of normal muscle metabolism. Because kidneys clear it at a near-constant rate, the serum level is a sensitive indicator of glomerular filtration. A rising creatinine signals declining kidney function; a falling creatinine in a known CKD patient indicates improvement (or muscle wasting).
Indian labs report serum creatinine in mg/dL and most also calculate eGFR (estimated Glomerular Filtration Rate) from the creatinine value plus age and sex — giving a percentage-style number that maps directly to CKD stages.
Why it matters
India has one of the highest CKD burdens in the world — driven by diabetes, hypertension, NSAID overuse and undiagnosed glomerular disease. CKD is silent until eGFR drops below ~30, by which point most damage is irreversible. A serum creatinine + eGFR is the simplest annual screen for early kidney disease, and is essential before contrast scans, before starting drugs that need renal dosing, and during any workup for swelling, blood-pressure changes, or unexplained fatigue.
How to prepare
No fasting required. Stay normally hydrated — severe dehydration raises creatinine, over-hydration lowers it. Avoid heavy meat consumption the day before (a large protein meal transiently raises creatinine). Avoid vigorous exercise in the 24 hours before testing — muscle turnover transiently elevates creatinine.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Serum Creatinine (mg/dL)[1][2] | Men 0.7 – 1.3 · Women 0.6 – 1.1 | Low creatinine usually reflects low muscle mass (elderly, vegetarian diet, prolonged illness, amputation) and is not in itself concerning. Use eGFR for a more accurate read of function in low-muscle states. | Creatinine above the reference range signals reduced kidney clearance. Acute rises (hours-days) — acute kidney injury from dehydration, drugs (NSAIDs, contrast, aminoglycosides), obstruction, or sepsis. Chronic rises (months-years) — chronic kidney disease. Pair with eGFR to stage the disease. |
| eGFR (calculated) (mL/min/1.73m²) | ≥ 90 normal · 60–89 mildly reduced · < 60 = CKD if sustained 3+ months | Below 60 sustained for 3+ months meets the definition of CKD. Stages: G3a (45–59), G3b (30–44), G4 (15–29), G5 (<15 — kidney failure). Each stage triggers specific monitoring and treatment changes. | Normal / high eGFR does not always rule out kidney disease — albuminuria can be present with normal eGFR (CKD stage 1 or 2). A urine UACR is the missing piece if there is diabetes, hypertension or family history. |
CKD stages by eGFR (KDIGO 2024)
| Stage | eGFR | Description | Action |
|---|---|---|---|
| G1 | ≥ 90 | Normal (CKD only if albuminuria or structural damage) | Treat underlying cause; monitor annually |
| G2 | 60–89 | Mildly reduced (CKD if markers of damage) | Treat cause; monitor annually |
| G3a | 45–59 | Mild to moderate | BP control, ACE-i/ARB, SGLT2 if diabetic; monitor every 6 months |
| G3b | 30–44 | Moderate to severe | Nephrology referral; anemia + bone disease screening; monitor quarterly |
| G4 | 15–29 | Severe | Prepare for renal replacement: vascular access, transplant evaluation |
| G5 | < 15 | Kidney failure | Dialysis or transplant required |
Frequently asked questions
Do I need to fast for a serum creatinine test?
No — fasting is not required. Avoid a heavy meat meal the night before and vigorous exercise on the test day, as both transiently raise creatinine.
My creatinine is 1.4 — do I have kidney disease?
A single mildly raised value is not diagnostic. The eGFR matters more — if eGFR is below 60 and stays below 60 on repeat in 3 months, that meets CKD criteria. Pair with a urine UACR and your doctor will interpret in context (age, muscle mass, hydration, medications).
Why does my muscle mass matter?
Creatinine comes from muscle. Heavily muscular adults can have creatinine slightly above the reference range without any kidney disease; the elderly or anyone with low muscle mass can have a "normal" creatinine despite reduced kidney function. eGFR accounts for age and sex but not for unusual body composition — so the result must be interpreted clinically.
Can dehydration raise creatinine?
Yes — significant dehydration raises both urea and creatinine and gives a falsely low eGFR (a "pre-renal" pattern). A high BUN/Creatinine ratio (>20) suggests dehydration rather than true kidney disease. Re-test after hydration if values are mildly off.
How often should I test serum creatinine?
Annually for anyone with diabetes, hypertension, family history of kidney disease, regular NSAID use, or age 60+. Every 3–6 months once CKD is diagnosed or while on kidney-relevant medication.
Will a single high creatinine on a hot day mean anything?
A single mildly raised creatinine after vigorous exercise or in dehydration usually returns to normal after rest and hydration. Repeat in a week and re-interpret. Pattern over time matters more than a single value.
What is the difference between creatinine and BUN?
Creatinine reflects muscle metabolism and kidney clearance, varying little with diet. BUN (urea) reflects protein breakdown and is much more affected by diet, hydration, and GI bleeding. The ratio between them helps distinguish kidney causes from pre-renal causes — ratio > 20 favours pre-renal (dehydration, GI bleed).
Should I do creatinine alone or a full KFT?
A full Kidney Function Test (KFT) — including BUN, electrolytes, uric acid, calcium, phosphorus and eGFR — gives more information for the same blood draw. Standalone creatinine is enough for an annual surveillance check if you have no risk factors.
Related Kidney / Electrolytes tests
Tests commonly ordered alongside CREATININE - SERUM, or that help interpret an unexpected result.
Sources & references
- KDIGO 2024 CKD Guideline · accessed 2026-05-29T00:00:00.000Z
- NIH MedlinePlus — Creatinine Test · accessed 2026-05-29T00:00:00.000Z
- National Kidney Foundation — eGFR · accessed 2026-05-29T00:00:00.000Z
- NCBI StatPearls — Creatinine · accessed 2026-05-29T00:00:00.000Z
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